Capacitive sensor and detection device with capacitive sensors for the detection of an obstruction situation

ABSTRACT

A capacitive sensor, in particular for the detection of an obstruction of objects or body parts by motor driven devices, includes an arrangement of a multitude of electrodes on a support and means to measure a capacitance or a capacitance change. The sensor is of a flat and film-like embodiment with a support made out of a film material for the arrangement of the electrodes. Furthermore, a capacitive sensor system, for detection of an obstruction situation of objects or body parts with motor driven devices uses several sensors of the above design, is disclosed, whereby an obstruction situation is detected, if a selection of several sensors is responding.

REFERENCE TO RELATED APPLICATION

This application is a U.S. national phase filing under 35 U.S.C. §371 ofPatent Cooperation Treaty No. PCT/DE2003/003443, filed Oct. 17, 2003,which claims priority to German Patent Application No. 10248761.8, filedOct. 18, 2002, the entire content of all of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to a capacitive sensor with an arrangementof a multitude of electrodes on a support and with means to measure acapacitance or a capacitance change. Furthermore, the invention concernsa detection device with a capacitive sensor system for the detection ofan obstruction of objects or body parts in motor driven devicescomprising several capacitive sensors according to the invention.

BACKGROUND OF THE INVENTION

With power-operated devices there is always the risk that objects orbody parts are caught, which can cause damage to objects or injury topeople. Since the use of motor driven devices is becoming more prevalentin order to enhance comfort, for example in doors, windows, and shuttersin building services engineering or in windows, sliding roofs, andconvertible tops in automotive engineering, an early and reliabledetection of an obstruction situation becomes increasingly important,since the movement of those devices often takes place automatically andwithout being monitored by an operator.

For example, newer convertible vehicles are often equipped with amovable convertible top, which can be automatically moved for examplefrom an open to a closed position or vice versa with the push of abutton. The movement of the convertible top is usually effected by ahydraulic drive, which in turn drives a convertible top mechanism, whichincludes a convertible top linkage. The linkage may support for atextile roof or a so-called hard-top folding roof with mainly rigid roofelements, and may include a cover for a convertible top compartment aswell as all elements that are being moved in the process by thedescribed parts.

Furthermore it is common knowledge to provide a detection device withcapacitive sensors in order to recognize an intervention into the rangeof motion of a motor driven device such as the convertible top.

Such an obstruction sensor with a capacitive sensor system is describedin German Patent Application DE 198 36 056 A1, whereby the device thatis being used to detect the obstructions, in particular whenautomatically closing convertible tops, vehicle windows or the likeincludes a capacitive sensor device, which consists of anelectroconductive transmitter surface on one side and anelectroconductive sensor wire and at least one metal surface that ismainly potential-free on the other side of an insulator. The transmittersurface and the sensor wire are connected to an electronic analysiscircuit in the process.

However, the disadvantage of these kinds of obstruction sensor devicesthat operate with a capacitive sensor system is that they require arelatively large installation space and thus can not be used in allsafety-relevant areas, which has the result that an obstructionsituation may not be detected until very late in the process when makingcontact with the object that interferes with the range of motion,whereupon a corresponding reaction can be triggered.

German Patent Application DE 101 04 333 A1 describes a convertiblevehicle with a convertible top which can be folded into a storagecompartment, whereby the storage compartment is located in a rear partof the vehicle adjacent to a trunk and is separated from the trunk bymeans of a variable separation device. The separation device is movablebetween a convertible top storage position in which it limits theadditional space and increases the storage compartment space, and aluggage storage position in which it limits the additional space andincreases the trunk space, whereby the separation device comprises atleast one movable plate element.

A capacitive sensor comprising a multitude of flat films is mounted onthe plate element in order to avoid an obstruction in the additionalspace during convertible top movement. This type of sensor comprises twofoils or plates arranged parallel to each other with a dielectricbetween. The dielectric is made out of a mechanically robust as well aselastically deformable material such as foamed material. A deformationof the sensor and thus a change of the distance between the foils orplates which can be measured as a change in capacitance that takes placewhen the sensor contacts a piece of luggage.

Although such a film-like sensor has the advantage to be flat incomparison with other sensors, the sensor needs to contact an obstaclein the path of motion. Therefore, also with this solution a reaction islate, especially in regard to an obstruction protection for body parts.

German Patent Application DE 40 11 901 A1 describes another capacitivesensor responding upon pressure, whereby a change in capacitanceresulting from a deformation of two parallel plates is measured.

Other capacitive sensors are known from German Patent PublicationsDE19724168C1, DE19805928A1, and DE3236056A1.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a capacitivemeasuring sensor, which can also be used when there is littleinstallation space available and permits a contact-less detection of anobject that is endangered to get into an obstruction situation, and toprovide a detection device with a capacitive sensor system, which makesit possible to detect an interference into the range of motion of amotor-driven device in all safety-relevant areas, whereby detectionshould take place reliably and as early as possible.

According to the invention, this object is solved with a capacitivesensor with the features described herein and a detection device withthe features described herein.

The capacitive measuring sensor according to the invention, which isshaped flat and film-like using a support made of film material for thearrangement of the electrodes, whereby the electrodes are arranged onone side of the support and ambient air is used as the dielectric inorder to achieve a contact-less detection of an object or a body part,has the advantage that it only requires very little installation spaceand that it can be also placed into difficult installation spacesbecause it can be deformed in all directions. It has the furtheradvantage that it permits contact-less obstruction detection due to thedielectric change created by the air, which makes the sensor mostsuitable for the obstruction detection in the path of motion of aconvertible's top.

The detection device according to the invention, with a capacitivesensor system for detecting whether objects or body parts are caught inmotor driven devices with several capacitive sensors according to theinvention, has the advantage that a clear distinction can be madebetween a capacitance change of all sensors that is caused by ambientconditions, e.g., due to a change in air humidity, and a capacitancechange due to an interference into the range of motion of the device,whereby only a selection of the capacitive measuring sensors that arebeing used are responding. The presence of an obstruction situation cantherefore be reliably detected.

The reliability of the output signal can be further increased byevaluating the dynamics of the capacitance change.

When they are advantageously used for a convertible top, the capacitivemeasuring sensors are appropriately located in critical areas ofconvertible top movement, such as in the area of elements that areconnected with each other by hinge-like connections such as elements ofthe convertible top linkage and/or a tensioning bow and/or a convertibletop compartment cover and/or a windshield frame and/or an area adjacentto a window. The space-saving arrangement between a sealing sectionand/or a trim part and its support is particularly advantageous.

To ensure reliable obstruction protection even if there is a malfunctionin the sensor system that is operating based on a certain measuringprinciple or if an obstruction situation is not detected or not detectedin time, it is advantageous if the capacitive sensor system of thedetection device described in the invention interacts with a sensorsystem that operates based on a different measuring principle in orderto recognize an intervention into the range of motion of the convertibletop mechanism, whereby the convertible top movement is controlled insafety mode via a control device after recognizing a fault in thedetection device or after detecting an obstruction situation. Thetransition into safety mode when the convertible top mechanism isactuated, by which a convertible top linkage and a convertible topcompartment cover, and if equipped with the related movable elements, isto be understood, ensures a reaction that is geared towards theparticular operating situation, which can consist of continuing theconvertible top movement with reduced speed or stopping or reversing theconvertible top movement.

An example of another sensor system operating based on a differentmeasuring principle is an optical sensor system.

Additional advantages and advantageous features of the invention will bereadily understood after reading the description, the drawings, and thepatent claims.

The drawings include a schematic of an application example of theinvention, which will be explained in further detail in the followingdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic view of only the convertible top of a convertiblevehicle;

FIG. 2 is a diagrammatic Figure of the design of a capacitive sensorsystem of a detection device; and

FIG. 3 is a flow chart of a normal mode and a safety mode for thecontrol of a convertible top movement with the aid of the capacitivesensor system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a movable convertible top 1 of a convertible. Theconvertible top 1 includes a convertible top mechanism 2, which can bemoved between an open and a closed position with the aid of a controldevice 3 representing a convertible top control unit and anelectro-hydraulic convertible top drive 4, of which only sections areshown in FIG. 1.

To be able to reliably carry out the automatic convertible top movementwithout the intervention of the vehicle user and without the user'ssupervision, an automatic detection device 5 is provided for thedetection of an interference into the range of motion of the convertibletop mechanism 2, which is here integrated into the convertible topcontrol unit 3 in terms of the electronic analysis unit.

The detection device 5 comprises a sensor system with sensors that carryout measurements based on different measurement principles, whereby partof the sensor system is designed as a capacitive sensor system 6 asshown in FIG. 2.

The presented capacitive sensor system 6 permits contact-lessobstruction recognition and is therefore particularly suited as part ofa multisensor system, such as the sensor system of the detection device5, which comprises, in addition to the capacitive sensor system 6, anoptical sensor system 7 that is shown only symbolically in FIG. 1.

FIG. 2 shows in principle a possible design of the capacitive sensorsystem 6, which has several capacitive sensors, a selection of which areshown with the capacitive sensors 8, 9, 10, and 11 in FIG. 2.

In the shown version, the capacitive sensors 8 to 11 are each located ina critical area of the convertible top mechanism 2, such as in an areaof elements 12, 13 which are connected with each other by hinges-likeconnections shown in FIG. 1, and which are elements of the convertibletop linkage, a tensioning bow 14, an area 15 next to a window, an area16 abutting to a windshield frame and in an abutting range for aconvertible top compartment cover, for which reference 17 shows themounting area in FIG. 1.

As shown schematically in FIG. 2, each of the present capacitive sensors8 to 11 is designed as a flat, film-like sensor, on which electrodes 18are located on a support of film material. The special structure of theconductor tracks on this film results in a capacitive sensor, which onone side of the film reacts upon a dielectric change, which is air forthe capacitive sensors 8 to 11. Thus, capacitance is changing when anobject or a body part approaches, which is converted into an analogvoltage signal in an integrated electronic circuit for furtherprocessing in the control unit 3 of the convertible top 1.

As appears from FIG. 2, the film-like sensors 8 to 11 are each connectedto the convertible top control unit 3 via an amplifier or transistor 19,20, 21, 22, whereby an automatically readjusting amplifier thresholdswitch 23 is provided between the transistors 19 to 22 and theconvertible top control unit 3 in the depicted version. There-adjustable amplifier 23 for instance causes, in the event of a sharpincrease of air humidity in the environment, such as in the event ofcontact with snow, an offset (change) of the switch point (zero-point)of all sensors, so that a body part such as a finger can be detectedeven through snow. The amplifier circuits 19 to 22 that are allocated toindividual sensors 8 to 11 are also arranged on the film material.

The capacitive sensor films 8 to 11, which are mounted between sealingsor trim parts of the convertible top mechanism 2 and their support asfar as possible, are able to detect a foreign object at a distance of upto 60 mm for example.

To rule out that the system is being triggered erroneously due toexternal influences, the sensors 8 to 11 that are used are compared, andthe plausibility of their signals is checked by an appropriateelectronic analysis device of the detection device 5 or the convertibletop control unit 3. In the event of a capacitance change of allcapacitive sensors the system assumes that the environmental influenceshave changed, whereby an obstruction situation is detected when thecapacitance changes in a selection of the capacitive sensors.

As soon as a fault is detected in detection device 5 or the previouslydescribed sensor system detects an obstruction situation during theconvertible top motion, the convertible top motion is controlled insafety mode, which is shown in further detail in FIG. 3, and in whichthe convertible top motion continues with reduced speed and power, isstopped, or is reversed in part or completely.

As appears from the flow chart in FIG. 3, an automatic start of theconvertible top motion is triggered in order to close the convertibletop 1 in a first step S1, when in the described example a defined amountof water is detected by a rain sensor.

After the start of the automatic convertible top motion, in a secondstep S2 is checked, whether the present optical sensor system 7 isfunctional. If the system is functional, a processing function S3defined for normal mode is started, in which normal mode convertible topmechanism 2 is driven with maximum power and speed.

In the process, an inquiry function S4 constantly checks whether theconvertible top 1 has already reached the final position. If this is thecase, the system proceeds with a processing function S15 that ends themonitoring function. Otherwise, the convertible top 1 continues with theclosing motion with the aid of a further processing function S5, wherebythe system permanently uses an inquiry function S6 to check during themotion, whether an obstruction is detected using the optical or thecapacitive or another sensor system.

In the event of a positive inquiry result of inquiry function S6, inother words when an obstruction situation is detected, the convertibletop motion is stopped at first by means of a subsequent processingfunction S7 and a waiting time is started. An inquiry function S8, whichis also called “Timeout” function, is used to check whether theobstruction situation is still present while the convertible top motionis stopped.

If the obstruction situation is no longer present, the system returns toinquiry function S4 in order to check whether the final position of theconvertible top 1 has been reached, otherwise a continuing convertibletop motion is permitted via function S5.

If the result of inquiry function S8 is that the obstruction situationis still present after the waiting time has ended and while theconvertible top motion is stopped, the system is started in safety modeby a processing function S9. This safety mode is also started if inquiryfunction S2 detects that the optical sensor system 7 is not functionalimmediately after the automatic convertible top motion starts.

After starting in safety mode, an inquiry function S10 checks, as innormal mode, whether convertible top 1 has reached its final position.If this is already the case, the system branches off to function S15,which ends the monitoring function. Otherwise, the convertible topmotion continues via a processing function S11 with reduced speed v_min,whereby an inquiry function S12 is used to check during this deceleratedconvertible top motion whether an obstruction situation is detected viathe capacitive sensor system 6. If this is not the case, the systemreturns to inquiry function S10 and the convertible top is closed withreduced speed until it has reached its final position.

If an obstruction situation is detected by inquiry function S12 insafety mode, the convertible top motion is stopped or reversed using aprocessing function S13 depending on the severity of the obstructionsituation, whereby a waiting time is started in a further step S14,during which the system checks whether the obstruction situation isstill present. As long as this is the case, the convertible top motionremains stopped or reversed.

With the aid of the safety mode it can be ruled out that the automaticfunction of the convertible top motion is not started due to a singleerror and that the vehicle is possibly damaged as a result ifapplicable. On the other hand, an adequate reaction is triggeredimmediately in the event of a clear obstruction situation.

It shall be understood that the presented capacitive measuring sensorcan be equipped with any arrangement of electrodes that is suitable forthe particular application and the capacitive sensor system can be used,with the corresponding modifications, for numerous other applicationssuch as in building services engineering or automotive engineering.

1. A detection system for detecting whether objects or body parts areobstructing a motor driven device, the system comprising: a plurality ofsensors, each sensor including: a generally flat and film-like support;a multitude of electrodes arranged on one side of the support; and ameans to measure a capacitance or a capacitance change; wherein ambientair represents the dielectric; a control in communication with theplurality of sensors, the control indicating a change in ambientconditions when all of the plurality of sensors measure a capacitancechange and the control indicating an obstruction situation when lessthan all of the plurality of sensors measure a capacitance change; andwherein each of the plurality of sensors can be deformed in alldirections for installation.
 2. A system according to claim 1, whereineach sensor further comprises an automatically readjusting thresholdswitch.
 3. A system according to claim 1, wherein the motor drivendevice, for which an obstruction of objects or body parts is detected,is a convertible top of a convertible vehicle.
 4. A system according toclaim 3, wherein the sensors are located in the area of elements thatare connected with each other by hinge-like connections and that areelements selected from a group consisting of a convertible top linkage,a tensioning bow, a convertible top compartment cover, a windshieldframe, and an area adjacent to a window.
 5. A system according to claim3, wherein one of the sensors is located between a sealing section ortrim part and a support.
 6. A system according to claim 3, furthercomprising an additional sensor system that uses measurements based on adifferent measuring principle in order to detect an interference intothe range of motion of the convertible top mechanism wherein, after amalfunction of the sensor system or an obstruction situation isrecognized, the convertible top motion is controlled by a control devicein a safety mode, in which the convertible top motion continues withreduced speed and power or is stopped or reversed.
 7. A system accordingto claim 6, wherein the additional sensor system comprises an opticalsensor system.
 8. A system according to claim 7, wherein the safety modeis started when a malfunction is recognized in the optical sensorsystem.
 9. A system according to claim 1, wherein the support of atleast one of the sensors is mounted to an element of a convertible top.